The TGC slide switches (20) which provide the TGC control of an ultrasonic diagnostic imaging system have LEDs (10) mounted on the sliders (22) of the slide switches so that the switches can be easily visualized in a darkened room. The light emitted by the LED of a switch is changed to an indicative color or brightness when the slider of the switch is set in its default position (36) for the application of a nominal gain to echo signals received from a given depth.
